Lined cylinder for internal combustion engines



Jan. 12, 1965 L. J. LECHTENBERG 3,165,094

LINED CYLINDER FOR INTERNAL COMBUSTION ENGINES Filed Oct. 5, 1962 United States Patent Ofi ice 3,165,094 Patented Jan. 12, 1965 3,165,094 LINED CYLINDER FOR INTERNAL COMBUSTIQN ENGINES Leo J. Lechtenherg, Elm Grove, Wis., assignor to Briggs & Stratton Corporation, Milwaukee, Wis a corporation of Delaware Filed Oct. 5, 1962, Ser. No. 228,542 9 Claims. (Cl. 12341.69)

This invention relates to internal combustion engines and refers more particularly to liners for the cylinders of such engines.

There is, of course, nothing new in the broad concept of providing a liner for an engine cylinder, and in the case of cylinders that are cast of aluminum it is customary to use a ferrous metal liner, unless the piston is chrome-plated, as in the Lechtenberg Patent No. 2,693,- 789. Usually, the cylinder liners were made of cast iron, though it was recognized that liners made of sintered iron by the briquetting technique were superior to cast iron liners. Their superiority resided not only in the far greater dimensional accuracy,'but also in the lubricant retention capability which characterizes the somewhat porous though very hard structure of briquetted sintered iron. However, despite these and other advantages of cylinder liners made of sintered iron, engine manufacturers have not seen fit to adopt them in production. The reason is cost.

Cost is a vital factor in the commercial production of engines, especially the smaller single cylinder engines in which a difference of a few cents in the selling price often determines whether an engine can be sold. Since the cost of producing a part by the powdered metal briquetting technique is appreciably higher than ordinary casting, and since this cost rises steeply as the size of the part increases, mere duplication in sintered iron of the prior cast iron liners, which extended for the full length of the cylinder bore and hence were quite large, was costwise prohibitive.

It is, therefore, the purpose of this invention to reduce the cost of providing a ferrous metal liner in a cylinder cast of aluminum,ror other non-ferrous metal and there by make it commercial practicable and economically feasible to provide such cylinder castings with liners of sintered ferrous metal.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein-disclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of the invention, constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

The single figure is a longitudinal sectional view through a portion of an engine, such as that of the Lechtengerg Patent No. 2,693,789, equipped with a cylinder liner in accordance with this invention, and illustrating the piston of the engine in full lines at one extremity of its travel, and in broken lines at the other extremity thereof.

As stated hereinbefore, the use of ferrous metal cylinder liners for an aluminum engine is not new. It is shown, for instance, in the Kunzog Patent No. 3,000,370, and in the earlier Stuckert Patent No. 2,573,116. However, when ferrous metal liners have been used prior to this invention they have always extended for the full length of the cylinder. Apparently it never occurred to anyone that this did not have to be, and that significant savings could be effected by having the liner only long enough to span the distance traversed by the piston rings, especially if the liner is made of sintered iron.

The wear which a cylinder wall takes during operation of the engine is fairly well concentrated to the portion thereof traversed by the piston rings. That part of the cylinder which lies below or inwardly of the lower or inner extremity of the piston ring travel receives very little wear, and even if worn does not haveany serious effect upon the operation of the engine.

Accordingly, the sintered iron cylinder liner 5 in the present invention extends only for that portion of the cylinder length needed to encompass the full travel of the rings 6 of the piston 7. Only the skirt of the piston rides upon and is guided by the unlined portion of the cylinder bore.

To accommodate and locate the shorter liner 5, the bore of the aluminum cylinder casting or block has a large diameter outer portion 8 and a smaller diameter inner portion 9, with an abrupt shoulder or step 10 therebetween. The liner 5 is seated in the large diameter portion 9 with its inner end abutting the shoulder 10. The inside diameter of the liner is substantially the same as that of the small diameter portion 9 of the casting, so that there is no perceptible change in the inside diameter of the cylinder bore along the entire length thereof.

The outside diameter of the liner 5 is uniform. Accordingly, if it becomes necessary or is desirable to replace the liner due to excessive wear, this can be done by threading an easy-out or other suitable similar tool into the liner and pulling on the tool while the casting is firmly held.

It is particularly significant that, when the liner is in place, one end thereof abuts the shoulder 10 while the opposite end thereof is flush with the outer face 11 of the cylinder casting, so that upon securement of the cylinder head 12 to the cylinder casting, the liner will be securely clamped between the cylinder head and the shoulder 10, it being understood that where a cylinder head gasket 13 is used, it will overlie the adjacent end of the liner 5 as well as the outer face of the cylinder casting. The cylinder liner is thus firmly and positively held in place.

The sintered iron liner 5 may be assembled with the cylinder casting, either by being shrunk or pressed into the large diameter portion 8 of the casting, or by being inserted into the die-casting mold and having the aluminum cast around it.

It should be apparent from the foregoing that by having the length of the cylinder liner only slightly greater than the distance traversed by the piston rings, sever-a1 important advantages are achieved. Foremost, of course, is the fact that the cost of the liner is considerably less than it would be if it extended for the full length of the cylinder bore.

Another advantage gained by the shorter liner is that it reduces the problems that might arise in its production. When an article such as a cylinder liner is made of sintered iron, the greater its length-to-diameter ratio is, the more diilicult it is to fill the die uniformly, and to obtain uniform density in the briquetted article. Again, after the article has been briquetted, its ejection from the die is more difficult the longer it is. Accordingly, by making the liner only long enough to have it encompass the travel of the piston rings, many of the deterrents to the use of sintered iron cylinder liners are overcome.

A further advantage of having the liner 5 terminate a substantial distance above or outwardly of the inner end of the cylinder bore has to do with cooling. Since the piston is made of aluminum, very good heat transfer takes place between its skirt and the unlined portion of the J cylinder bore, with the result that the piston is cooled much more effectively than it could be if the sintered ferrous metal -liner 5 extended for the full length of the bore. Also, the cooling fins 14 on the cylinder wall need not extend beyond the lined portion of the cylinder.

It' is, of course, desirable to have good heat transfer from the liner to the surrounding casting. This is best assured by leaving the liner just as it is formed, i.e. not treated in any way which would close its pores, and casting it in place. When thus assembled with the aluminum casting, the aluminum penetrates into the pores of the sintered iron and produces a junction which approaches homogeneity.

In any event, if the liner is subjected to a steam treat-- ment, its wear resistance is improved.

Since the steam treatment effectually closes the pores of the sintered iron, liners that are so treated are held in place principally by being confined between the shoulder l0 and the cylinder head.

From the foregoing description taken with the accompanying drawings, the advantages achieved by this invention should be apparent to those skilled in this art. It should also be obvious that while aluminum has been specifically mentioned as the metal from which the cylinder casting is formed, other non-ferrous metals, such as magnesium, could be used therefor.

What is claimed as my invention is:

1. In .a cyilnder block assembly, for an internal combustion engine including a removable cylinder head and a reciprocating skirted piston including at least two spaced piston rings thereon, the combination comprising, a cylinder block formed from cast aluminum and having a bore extending Within said block formed with two concentric ditferent diameters therein with a shoulder there between, a sintered iron cylinder liner removably fitted into the larger diameter portion of said bore and abutting said shoulder, the inner diameter of said liner being substantially equal to the smaller diameter portion of said bore for forming a substantially continuous cylinder wall therewith when the liner is in place, said liner extending within said cylinder bore a distance only slightly greater than the distance traversed by said piston rings, whereby the piston rings bear against the liner during normal reciprocation of the piston, the skirt of the piston being guided by the unlined portion of the cylinder bore, said liner being clamped against said shoulder by said cylinder head.

2. The assembly claimed in claim 1 wherein cooling fins are cast on the outside of said block and extend thereon only through that portion which is adjacent the said liner.

3. The assembly claimed in claim 1 wherein the cylinder block has a substantially uniform thickness throughout.

4. In an internal combustion engine including a cylinder head, a cylinder block assembly for use with a reciprocating piston of predetermined stroke having piston rings thereon, the combination comp-rising, a cast aluminum shell having a bore therethrough, a relatively thin metal liner for said bore removably positioned therein, said liner only extending within said here over that portion traversed by the piston rings, and means for positively positioning said liner within said bore.

5. The assembly claimed in claim 4 wherein the said liner is clamped against displacement when the cylinder head is attached to the block.

6. The assembly claimed in claim 4 wherein the said liner is sintered metal.

7, In an internal combustion engine of the type wherein a piston equipped with piston rings reciprocates with a fixed stroke in the bore of a cylinder, the improvement which comprises the combination of: a non-ferrous metal cylinder casting having a bore; a relatively thin metal liner for said bore positioned therein, said liner encompassing only that portion of the length of the bore traversed by the piston rings; and means for positively positioning the liner in the bore.

8. In an internal combustion engine, the improvement set forth in claim 7, wherein the liner is sintered metal.

9. In an internal combustion engine, the improvement set forth in claim 8, wherein the non-ferrous metal of the cylinder casting penetrates into the pores of the sintered liner, to thereby improve the heat transfer between the liner and the surrounding casting and assist in securing the liner in place.

No references cited. 

1. IN A CYLINDER BLOCK ASSEMBLY, FOR AN INTERNAL COMBUSTION ENGINE INCLUDING A REMOVABLE CYLINDER HEAD AND A RECIPROCATING SKIRTED PISTON INCLUDING AT LEAST TWO SPACED PISTON RINGS THEREON, THE COMBINATION COMPRISING, A CYLINDER BLOCK FORMED FROM CAST ALUMINUM AND HAVING A BORE EXTENDING WITHIN SAID BLOCK FORMED WITH TWO CONCENTRIC DIFFERENT DIAMETERS THEREIN WITH A SHOULDER THEREBETWEEN, A SINTERED IRON CYLINDER LINER REMOVABLY FITTED INTO THE LARGER DIAMETER PORTION OF SAID BORE AND ABUTTING SAID SHOULDER, THE INNER DIAMETER OF SAID LINER BEING SUBSTANTIALLY EQUAL TO THE SMALLER DIAMETER PORTION OF SAID BORE FOR FORMING A SUBSTANTIALLY CONTINUOUS CYLINDER WALL THEREWITH WHEN THE LINER IS IN PLACE, SAID LINER EXTENDING WITHIN SAID CYLINDER BORE A DISTANCE ONLY SLIGHTLY GREATER THAN THE DISTANCE TRAVERSED BY SAID PISTON RINGS, WHEREBY THE PISTON RINGS BEAR AGAINST THE LINER DURING NORMAL RECIPROCATION OF THE PISTON, THE SKIRT OF THE PISTON BEING GUIDED BY THE UNLINED PORTION OF THE CYLINDER BORE, SAID LINER BEING CLAMPED AGAINST SAID SHOULDER BY SAID CYLINDER HEAD. 